President Barack Obama, noting the more than 300,000 firearm-related US deaths over the past decade, announced executive orders Tuesday aimed at reducing gun violence.

The “commonsense” reforms, which bypass the Republican-controlled Congress, are opposed by critics, including Republican 2016 presidential hopefuls who argue that Obama’s unilateral actions violate the US Constitution and restrict law-abiding citizens’ access to firearms.

Here are key elements of Obama’s executive actions:

– Requiring background checks

The core of Obama’s move involves firming up the existing system for conducting background checks on gun sales, notably by closing the “gun show loophole” which exempts dealers at gun shows or online from conducting a background check before selling a weapon.

– Strengthening background check system

Authorities will act to make the National Instant Criminal Background Check System (NICS) more efficient, including improving state reporting to the system, hiring 230 more examiners to swiftly process checks around the clock, and modernizing digital aspects of NICS.

– Licenses for all sellers

Anyone “engaged in the business” of selling firearms must now be licensed as a dealer, which would require that person or entity to perform background checks for all gun sales.

There is no specific threshold that triggers the licensing requirement, and those who sell exclusively online or at gun shows can be considered dealers just as is a person running a brick-and-mortar store. Failure to comply with licensing requirements may result in a five year prison sentence and a $250,000 fine.

– Expanding mental health treatment

“Significant” new resources are being dedicated to boosting access to mental health care, including a $500 million proposal to increase service capacity, and ensuring that people with mental illness are prevented from acquiring guns. The Social Security Administration is to ensure that those with documented mental health issues are reported into NICS.

– Reporting mentally ill patients

The reforms enable health care providers to report names of mentally ill patients into the background check system. Health care privacy rules prevent doctors from sharing such data without consent of their patients, but the administration rules now allow health care providers to report to the NICS “limited demographic and other necessary information about these individuals.”

– Improving gun law enforcement

US Attorney General Loretta Lynch is vowing to conduct “smart and effective enforcement” of existing gun laws, including tracking illegal online firearms trafficking and enhancing the ballistics system that can help investigators link violent crimes across jurisdictions. Obama’s 2017 budget will include funding for 200 new agents to help enforce gun laws.

– Researching gun-safety technology

Obama wants to boost research efforts to improve “smart gun technology,” and has directed the Pentagon, Justice Department, and Department of Homeland Security to increase research on technology that would reduce accidents and improve tracing of lost or stolen guns. The agencies must report back to Obama in 90 days with strategy outlines.

– Combating domestic violence

Lynch issued a memo to US Attorney’s Offices to renew domestic violence outreach efforts. The goal is to provide additional resources for state, local and tribal law enforcement and for community groups to help fight the scourge and prevent domestic abusers from obtaining guns.